Process for the manufacture of high-purity n-paraffins

ABSTRACT

A process for the manufacture of high-purity n-paraffins from mixed straight and branched chain hydrocarbons achieved through a primary adduction step followed by alkylation.

United States Patent 1111 [72] Inventor Donald M. Little [56] References Cited Okll- UNITED STATES PATENTS 3 1 1969 2,396,853 3/1946 Jones 260/683.49 [221 ed d 2 1971 3,078,321 2/1963 Van Pooletal. 260168349 [451 1 3,190,935 6/1965 Hutson 260/676 [731 Asslgnee 3,443,040 6/1969 Little et al. 208/308 Primary Examiner- Herbert Levine 54 access FOR THE MANUFACTURE OF HlGll- Attorney-Young and Quigg PURITY N-PARAFF INS 3 Claims, 1 Drawing Fig.

52 us. 01 208/85, 208/308, 260/676, 260/683.49 [5 1] Int. Cl C103 29/22, ABSTRACT: A process for the manufacture of high-purity 11- C070 9/14 paraffins from mixed straight and branched chain hydrocar- [50] Field 0! Search 208/85, bons achieved through a primary adduction step followed by 308; 260/676, 683.4, 683.43, 683.48, 683.49 alkylation.

HC FEED 2 AROMATIC HC 5 Q 1 UREA-SULFOLANE 9 us CHARGE 3 TREATING ZONE ISOPARAFFINIC HC 22 HEAVY ALKYLATE PATENTEnunv 2 I9?! HC FEED T v2 us CHARGE 3 UREA- SULFOLANE TREATING ZONE AROMATIC HC 8 ISOPARAFFINIC HCS n-PARAFFIN5 24 22 HEAVY ALKYLATE INVENTOR. D. M. LIT TLE A T TORNE Y5 PROCESS FOR THE MANUFACTURE OF HIGH-PURITY N-PARAFFINS This invention relates to a process for the manufacture of high-purity n-parafi'ins.

The urea process for selectively adducting straight chain hydrocarbons is known in the art. The straight chain hydrocarbons are separated according to the prior art, U.S. Pat. No. 3,448,040, by the fonnation and subsequent decomposition of the urea hydrocarbon adduct in the presence of a sulfolane compound.

The prior art in order to reach a n-parafi'ln purity of above 95 percent by volume through a urea adduction process would require a plurality of adduction, settling and separation stages. The urea adduction process removes most of the aromatics and the naphthenics but allows a relatively large volume of isoparaffins to remain in the partially enriched n-paraffin stream. A second and subsequent stages are required for the further enrichment of the n-paraffins from about 80 percent to at least 95 percent by volume. The poor efficiency of the secondary stages of the urea adduction process is due to the problem of removing isoparaffins from the normal paraffins.

Olefinic alkylation as an independent method of n-paraffin enrichment is not a satisfactory method due to the large volume use of low boiling olefins and the resulting highvolume production of heavy alkylates. if olefinic alkylation is used as a primary stage, then the branched chain hydrocarbons are converted to heavy alkylates of low value as compared to the consumed low-boiling olefins.

It is an object of this invention to provide an improved process for the manufacture of high-purity n-paraffins.

l have discovered an improved method for the production of high-purity n-paraffins from a feedstream containing nparaffins, isoparaffins. and cyclo-hydrocarbons. My invention utilizes a primary separation step by the use of a urea adduction which produces a partially enriched stream of n-paraffins which contains a relatively large volume of isoparaffins. The partially enriched n-paraffins stream is then contacted with low-boiling olefins in the presence of suitable alkylation catalysts in order to alkylate the isoparaffins. The isoparaffins alkylation step is carried out under conditions which prevent the isomerization of the n-paraffins. The alkylation step is followed by separation which yields a high-purity enriched nparaffin stream.

Heretofore, neither the urea adduction nor the alkylationfractionation met the needs individually of efficiently producing enriched n-paraffins of at least 95 percent by volume purity even though a single adduction process can remove the bulk of the cyclo-hydrocarbons and a large portion of the isoparaffins.

According to the invention most of the remaining isoparaffins are removed by alkylation, thus efficiently producing a nparafiin stream of high purity. The alkylation-fractionation stage heretofore applied individually as the only method of nparaffin enrichment was not satisfactory due to the large volume use of costly olefins and the lack of efficiency under reaction conditions which prevent isomerization of the nparaffins. While both methods are known by the industry, the art has not achieved efficient production of high purity nparaffins through multiple staging.

A hydrocarbon feedstream containing n-paraffins, isoparaffins, and cycle-hydrocarbons of a l to 20 carbon atoms per molecule range can be used in my invention. Preferably a hydrocarbon feedstream of carbon atoms to 14 carbon atoms per molecule is used. High-purity n-paraffins of a l0 to 14 carbon atoms per molecule range are in good demand for use in the detergent industry. N-paraffins of a 10 to l4 carbon atoms per molecule range are used to produce biodegenerable detergent alkylate required by modern water pollution controls.

Broadly speaking, the feed is contacted with an amide to selectively adduct the n-parafiins. In one specific embodiment, the feed is contacted with a urea-sulfolane solution consisting of about 13 weight percent urea and about 87 weight percent sulfolane. The hydrocarbon feedstream is contacted with the urea-sulfolane solution at about F. under an approximate pressure of 5 p.s.i.g. for about 45 minutes. The hydrocarbon feed to urea-sulfolane feed ratio is approximately 1:3 by volume. The partially, urea-sulfolane enriched, nparafim stream consists of approximately percent n-paraffins, 10 percent isoparaffins and 5 percent aromatics, naphthenics and others by volume.

The urea-sulfolane reactor temperature and pressure can vary widely depending on the type of hydrocarbon being separated. Generally a temperature of about 75 to l25 F. and a pressure of about 5 to p.s.i.g. will be used during the formation of the adduct. The urea-sulfolane decomposition and phase separation zone will generally run at about a pressure of 5 to 20 p.s.i.g. and an approximate temperature range of to 240 F., the adduct normally breaks at around l60 F.

The partially enriched n-paraffin stream is then alkylated at a temperature preferably below 85 F. at a pressure sufficient to insure liquid phase for about 2 minutes with a stream of olefins containing three to six carbon atoms per molecule in the presence of a conventional alkylation catalyst, for example, hydrofluoric acid, sulfuric acid, and/or aluminum halide. Upon fractionation of the alkylated stream a n-paraffin stream of at least 95 percent by volume purity is recovered. Unreacted olefins are recycled for alkylation feed and the resulting high-boiling alkylates are drawn off as heavies.

The alkylation reactor temperature can vary widely depending on the catalyst used and the hydrocarbon stream being alkylated. Generally a temperature range of 50 to I25 F. is required when using as an example hydrofluoric acid as the alkylation catalyst. When the alkylation catalyst is hydrofluoric acid, the catalyst is contacted in the alkylation zone with approximately a 1:! volume ratio of hydrocarbon charge.

Referring to the drawing a stream 2 of mixed straight and branched chain hydrocarbons along with aromatics and naphthenics, and a urea-sulfolane charge. stream 3, are fed into the urea-sulfolanertreating zone 4. A partially enriched nparaffinstream 6 is withdrawn from the urea-sulfolane-treating zone 4. The aromatic and naphthenic hydrocarbons are withdrawn by way of outlet 8. The isoparaffinic hydrocarbons are recovered by way of conduit 9.

The partially enriched n-parafftn stream 6 is fed into an alkylation zone 10 under minimum n-paraffm isomerization conditions. Under low-temperature alkylation in zone 10. minimum isomerization of the n-parafiin stream is found to exist. Olefms, boiling below the lowest boiling n-paraffins. of the range three to six carbon atoms per molecule, are introduced into zone 10 as shown by conduit ll and recycle conduit 12. A resulting alkylated n-paraffin stream 14 is recovered from zone 10 and is fed into the fractionation zone 16.

The fractionation zone 16 separates the high-boiling alkylate, for example the alkylates of olefins and isoparafiins, from the unreacted n-paraffins. The heavier high-boiling alkylate is withdrawn as shown by conduit 22 and the enriched n-paraffins are withdrawn as shown by conduit 24. Unreacted lowboiling olefins are withdrawn from the fractionation zone 16 as shown by conduit 18 as a recycle stream. Light inerts, saturated paraffins boiling in the range of the olefins, are removed by bleeding off a portion of the recycle olefins by way of conduit 20.

The drawing does not include equipment or process steps for each zone since the inclusion of such equipment and interim processes are understood by those skilled in the art and are within the scope of the invention.

EXAMPLE A fresh feed of hydrocarbons of the C to C carbon atoms per molecule range, comprising 20 percent by volume isoparaffins, 20 percent by volume n-paraffins, 30 percent by volume aromatics and 30 percent by volume naphthenics is introduced into the urea-sulfolane-treating zone as shown in FIG. 1. Thefeed is introduced at a rate of 1,000 barrels per day as compared to a urea-sulfolane charge of 3,000 barrels per day comprised of 13 percent by weight urea and 87 percent by weight sulfolane. The urea-sulfolane-treating zone requires a contact time of about 45 minutes and an approximate temperature of 80 F. under a pressure of about 5 p.s.i.g.

A partially enriched n-paraffin stream withdrawn from the urea-sulfolane-treating zone is comprised approximately of the following portionsby volume: percent isoparaffins, 85 percent n-paraffins, 2 percent aromatics, and 3 percent naphthenics by volume. The above stream is fed into the alkylation zone at a rate of about 220 barrels per day along with barrels per day of olefins consisting of three to six carbon atoms per molecule. The alkylation zone is maintained under sufi'rcient pressure to ensure liquid phase contacting of the above feedstream with a lzl feed ratio of hydrofluoric acid alkylation catalyst to hydrocarbon charge at an ambient temperature of 80 F. for approximately 2 minutes. The low-temperature alkylation process alkylates the isoparafi'ms containing 10 to 14 carbon atoms per molecule with the olefins containing three to six carbon atoms per molecule to produce alkylates which because of higher boiling points can be separated by fractionation, and minimizes isomerization of the n-paraffins to isoparaffins, while alkylating the nonstraight chain hydrocarbons. The alkylation-fractionation-separation zone yields approximately 177 barrels per day of n-parafiins with a purity of at least about 95 percent by volume.

What is claimed is:

l. A process for the manufacture of high-purity n-paraffins, comprising the steps of: admixing a stream of mixed branched chain and straight chain hydrocarbons with urea, thereby adducting the straight chain hydrocarbons;

decomposing the amide adduct;

separating a partially enriched n-parafi'm stream;

admixing the partially enriched n-parafiin stream with lowboiling olefins under minimum n-paraffin, isomerizationalkylation conditions in the presence of an alkylation catalyst;

separating the n-parafims from the resulting alkylate; and

recovering the enriched n-parafiin stream.

2. A process according to claim 1 whereby the stream of mixed branched chain and straight chain hydrocarbons consisting of 10 to 20 carbon atoms per molecule is admixed with a urea-sulfolane solution, the straight chain hydrocarbons are adducted as a urea adduct in the presence of a sulfolane solution, a partially enriched n-paraffin stream containing at least 10 percent isoparaffins is separated from the urea-sulfolane adduct by heat decomposition, said partially enriched n-paraffin stream is withdrawn and admixed with low-boiling olefins of three to six carbon atoms per molecule under minimum, nparaffin, isomerization-alkylation conditions in the presence of an alkylation catalyst, the n-paraffins are separated from the high-boiling alkylate and an n-paraffin stream of at least 95 percent by volume is recovered.

3. A process according to claim 1 whereby the stream of mixed branched chain and straight chain hydrocarbons con sisting of 10 to 14 carbon atoms per molecule, comprised of nparaffins, isoparaffins, aromatics, and naphthenics, is admixed with a urea-sulfolane solution, the straight chain hydrocarbons are adducted as a urea adduct in the presence of a sulfolane solution, a partially enriched n-paratfin stream containing at least percent by volume n-paraffins and at least 10 percent by volume isoparafi'ins is separated from the urea-sulfolane adduct by heat decomposition, the partially enriched n-paraffin stream is withdrawn and admixed with low boiling olefins of three to six carbon atoms per molecule under alkylation conditions below 85 F. in the presence of a hydrofluoric acid alkylation catalyst, the n-paraffns are separated fromthe high boiling alkylate, and a n-paraftin stream of at least percent by volume is recovered.

t II i i 

2. A process according to claim 1 whereby the stream of mixed branched chain and straight chain hydrocarbons consisting of 10 to 20 carbon atoms per molecule is admixed with a urea-sulfolane solution, the straight chain hydrocarbons are adducted as a urea adduct in the presence of a sulfolane solution, a partially enriched n-paraffin stream containing at least 10 percent isoparaffins is separated from the urea-sulfolane adduct by heat decomposition, said partially enriched n-paraffin stream is withdRawn and admixed with low-boiling olefins of three to six carbon atoms per molecule under minimum, n-paraffin, isomerization-alkylation conditions in the presence of an alkylation catalyst, the n-paraffins are separated from the high-boiling alkylate and an n-paraffin stream of at least 95 percent by volume is recovered.
 3. A process according to claim 1 whereby the stream of mixed branched chain and straight chain hydrocarbons consisting of 10 to 14 carbon atoms per molecule, comprised of n-paraffins, isoparaffins, aromatics, and naphthenics, is admixed with a urea-sulfolane solution, the straight chain hydrocarbons are adducted as a urea adduct in the presence of a sulfolane solution, a partially enriched n-paraffin stream containing at least 85 percent by volume n-paraffins and at least 10 percent by volume isoparaffins is separated from the urea-sulfolane adduct by heat decomposition, the partially enriched n-paraffin stream is withdrawn and admixed with low boiling olefins of three to six carbon atoms per molecule under alkylation conditions below 85* F. in the presence of a hydrofluoric acid alkylation catalyst, the n-paraffins are separated from the high boiling alkylate, and a n-paraffin stream of at least 95 percent by volume is recovered. 